Top emission microLED display and bottom emission microLED display and a method of forming the same

ABSTRACT

A microLED display includes a first main substrate, microLEDs disposed above the first main substrate, a first light blocking layer disposed above the first main substrate to define emission areas, a light guiding layer disposed in the emission areas, and a plurality of connecting structures disposed in the emission areas respectively and electrically connected with the microLEDs.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 16/128,255, filed on Sep. 11, 2018, the entire contents of which areherein expressly incorporated by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention generally relates to a light-emitting diode (LED)display, and more particularly to a top emission microLED display and abottom emission microLED display.

2. Description of Related Art

A micro light-emitting diode (microLED, mLED or μLED) display panel isone type of flat display panel, which is composed of microscopicmicroLEDs each having a size of 1-10 micrometers. Compared toconventional liquid crystal display panels, the microLED display panelsoffer better contrast, response time and energy efficiency. Althoughboth organic light-emitting diodes (OLEDs) and microLEDs possess goodenergy efficiency, the microLEDs, based on group III/V (e.g., GaN) LEDtechnology, offer higher brightness, higher luminous efficacy and longerlifespan than the OLEDs.

Active matrix using thin-film transistors (TFT) may be used in companionwith microLEDs to drive a display panel. However, microLED is made byflip chip technology, while TFT is made by complementarymetal-oxide-semiconductor (CMOS) process which is more complex than flipchip technology. These two distinct technologies may cause thermalmismatch. A drive current of the microLED is small in gray display,which may be significantly affected by leakage current.

Passive matrix is another driving method performed by a row drivecircuit and a column drive circuit, which are disposed on the peripheryof a display panel. When the size or the resolution of the display panelincreases, output loading and delay of the drive circuits increaseaccordingly, causing the display panel to malfunction. Therefore,passive matrix is not suitable for large-size microLED display panels.

A need has thus arisen to propose a novel microLED display panel,particularly a large-size or high-resolution display panel, which iscapable of maintaining advantages of microLEDs and overcomingdisadvantages of driving schemes.

As adjacent microLEDs are near to each other, interference (e.g., colormixing) between adjacent microLEDs may happen and thus decrease contrastratio. Moreover, non-uniform display may happen due to connecting wirescomposed of opaque or reflective material that connecting the microLEDswith other components or circuits.

A need has thus arisen to propose a novel microLED display with luminousefficacy improvement over the conventional microLED displays.

SUMMARY OF THE INVENTION

In view of the foregoing, it is an object of the embodiment of thepresent invention to provide structures and forming methods of a topemission microLED display and a bottom emission microLED display capableof prevent interference, color mixing and non-uniform display issues.

According to one embodiment, a top emission microLED display includes afirst main substrate; a bottom common electrode layer disposed on a topsurface of the first main substrate; a plurality of microLEDs disposedon the bottom common electrode layer; a first light blocking layerdisposed on the bottom common electrode layer to define a plurality ofemission areas; a light guiding layer disposed in the emission areas;and a plurality of connecting structures disposed in the emission areasrespectively and electrically connected with the microLEDs.

According to another embodiment, a bottom emission microLED displayincludes a first main substrate; a plurality of microLEDs disposed abovethe first main substrate; a first light blocking layer disposed abovethe first main substrate to define a plurality of emission areas; alight guiding layer disposed in the emission areas; a plurality ofconnecting structures disposed in the emission areas respectively andelectrically connected with the microLEDs; and a top common electrodelayer disposed above the first light blocking layer and the microLEDs.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows a side view of a top emission microLEDdisplay;

FIG. 2A shows a top view of a top emission microLED display according toa first embodiment of the present invention;

FIG. 2B shows a cross-sectional view of FIG. 2A;

FIG. 2C shows a cross-sectional view of a top emission microLED displayaccording to a modified first embodiment of the present invention;

FIG. 2D shows another top view of the top emission microLED displayaccording to the first embodiment of the present invention;

FIG. 3A shows a top view of a top emission microLED display according toa second embodiment of the present invention;

FIG. 3B shows a cross-sectional view of FIG. 3A;

FIG. 3C shows a cross-sectional view of a top emission microLED displayaccording to a modified second embodiment of the present invention;

FIG. 3D shows another top view of the top emission microLED displayaccording to the second embodiment of the present invention;

FIG. 4A shows a top view of a top emission microLED display according toa third embodiment of the present invention;

FIG. 4B shows a cross-sectional view of FIG. 4A;

FIG. 4C shows a cross-sectional view of a top emission microLED displayaccording to a modified third embodiment of the present invention;

FIG. 5A shows a top view of a top emission microLED display according toa fourth embodiment of the present invention;

FIG. 5B shows a cross-sectional view of FIG. 5A;

FIG. 5C shows a cross-sectional view of a top emission microLED displayaccording to a modified fourth embodiment of the present invention;

FIG. 6 shows a cross-sectional view of a top emission microLED displayaccording to a fifth embodiment of the present invention;

FIG. 7A to FIG. 13B show top views and cross-sectional viewsillustrating steps of forming a top emission microLED display accordingto one embodiment of the present invention;

FIG. 14 schematically shows a side view of a bottom emission microlight-emitting diode (microLED) display;

FIG. 15A shows a top view of a bottom emission microLED displayaccording to a sixth embodiment of the present invention;

FIG. 15B shows a cross-sectional view of FIG. 15A;

FIG. 15C shows a cross-sectional view of a bottom emission microLEDdisplay according to a modified sixth embodiment of the presentinvention;

FIG. 15D shows another top view of the bottom emission microLED displayaccording to the sixth embodiment of the present invention;

FIG. 16A shows a top view of a bottom emission microLED displayaccording to a seventh embodiment of the present invention;

FIG. 16B shows a cross-sectional view of FIG. 16A;

FIG. 16C shows a cross-sectional view of a bottom emission microLEDdisplay according to a modified seventh embodiment of the presentinvention;

FIG. 16D shows another top view of the bottom emission microLED displayaccording to the seventh embodiment of the present invention;

FIG. 17A shows a top view of a bottom emission microLED displayaccording to an eighth embodiment of the present invention;

FIG. 17B shows a cross-sectional view of FIG. 17A;

FIG. 17C shows a cross-sectional view of a bottom emission microLEDdisplay according to a modified eighth embodiment of the presentinvention;

FIG. 18A shows a top view of a bottom emission microLED displayaccording to a ninth embodiment of the present invention;

FIG. 18B shows a cross-sectional view of FIG. 18A;

FIG. 18C shows a cross-sectional view of a bottom emission microLEDdisplay according to a modified ninth embodiment of the presentinvention;

FIG. 19 shows a cross-sectional view of a bottom emission microLEDdisplay according to a tenth embodiment of the present invention;

FIG. 20A to FIG. 26B show top views and cross-sectional viewsillustrating steps of forming a bottom emission microLED displayaccording to one embodiment of the present invention;

FIG. 27 shows a cross-sectional view of a bottom emission microLEDdisplay according to an eleventh embodiment of the present invention;

FIG. 28 shows a cross-sectional view of a top emission microLED displayaccording to a twelfth embodiment of the present invention;

FIG. 29 shows a cross-sectional view of a bottom emission microLEDdisplay according to a thirteenth embodiment of the present invention;

FIG. 30 shows a cross-sectional view of a bottom emission microLEDdisplay according to a modified thirteenth embodiment of the presentinvention;

FIG. 31 shows a cross-sectional view of a bottom emission microLEDdisplay according to a fourteenth embodiment of the present invention;and

FIG. 32 shows a cross-sectional view of a bottom emission microLEDdisplay according to a modified fourteenth embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 schematically shows a side view of a top emission microlight-emitting diode (microLED) display 100. In the embodiment,microLEDs 12 (e.g., red microLED 12R, green microLED 12G and bluemicroLED 12B) may be disposed on a top surface of a main substrate 11 bya bonding technique. As the microLEDs 12 emit light upward (as shown byarrows) against the top surface of the main substrate 11, the display100 is called a top emission microLED display. In the specification, themicroLEDs 12 have a size of 1-10 micrometers, which may be decreased orincreased according to specific applications or technologicaldevelopment in the future.

FIG. 2A shows a top view of a top emission microLED display 200according to a first embodiment of the present invention, and FIG. 2Bshows a cross-sectional view of FIG. 2A. In the embodiment, microLEDs 22(e.g., red microLED 22R, green microLED 22G and blue microLED 22B) maybe disposed above a (first) main substrate 21A. A (first) light blockinglayer 23A is disposed between adjacent microLEDs 22 and above the(first) main substrate 21A to prevent interference (e.g., color mixing)between adjacent microLEDs 22 and to enhance contrast. A bottom commonelectrode layer 28 may be disposed between the main substrate 21A andthe microLEDs 22. In the present embodiment (and the followingembodiments), the microLED 22 may be a rectangle, for example, with alength of 25 micrometers and a width of 10 micrometers. According to oneaspect of the embodiment, the microLEDs 22 may be disposedlongitudinally. That is, the length of the microLED 22 is parallel tothe longitude of the display 200, and the width of the microLED isparallel to the latitude of the display 200. As human eyes are moresensitive to vertically emitted light than horizontally emitted light,the display 200 of the embodiment can enhance viewing angle.

The (first) light blocking layer 23A of the embodiment may include blackmatrix (BM). In the embodiment shown in FIG. 2B, black resin is firstformed, followed by adopting photo process and curing process to formthe BM (first) light blocking layer 23A. In another embodiment, ink-jetprinting technique and curing process are adopted to form the BM (first)light blocking layer 23A.

The (first) light blocking layer 23A defines emission areas 24, whichare not covered with the (first) light blocking layer 23A. In otherwords, areas other than the emission areas 24 are covered with the(first) light blocking layer 23A. A light guiding layer 25, composed oflight guiding material, is disposed in the emission areas 24 to spreadthe light emitted by the microLEDs 22. The light guiding material istransparent with high refractive index. In the embodiment, the lightguiding layer 25 is entirely formed in the emission areas 24.

In the embodiment, the (first) light blocking layer 23A has a thicknessgreater than the light guiding layer 25. Further, the light guidinglayer 25 has a thickness greater than or equal to the microLEDs 22.

FIG. 2C shows a cross-sectional view of a top emission microLED display200 according to a modified first embodiment of the present invention.In the embodiment shown in FIG. 2C, the (first) light blocking layer 23Ahas a thickness less than the light guiding layer 25. Moreover, the(first) light blocking layer 23A and the light guiding layer 25partially overlap each other, and the (first) light blocking layer 23Ais partially covered with the light guiding layer 25. In the embodimentshown in FIG. 2C, a chromium/chromium oxide film is first formed,followed by adopting photo etching technique to form the BM (first)light blocking layer 23A.

FIG. 2D shows another top view of the top emission microLED display 200according to the first embodiment of the present invention. A connectingstructure 26, such as conductive electrode, is disposed on a top surfaceof the microLED 22 in each emission area 24. The connecting structure 26may include transparent material (e.g., indium tin oxide), opaquematerial (e.g., metal) or reflective material. According to one aspectof the embodiment, the connecting structures 26 in the emission areas 24have the same pattern, which can prevent nonuniform display issue.

FIG. 3A shows a top view of a top emission microLED display 300according to a second embodiment of the present invention, and FIG. 3Bshows a cross-sectional view of FIG. 3A. The second embodiment issimilar to the first embodiment with the exception that, in the secondembodiment, the (first) light blocking layer 23A is disposed betweenadjacent pixels (instead of adjacent microLEDs 22) to preventinterference (e.g., color mixing) between adjacent pixels and to enhancecontrast.

The (first) light blocking layer 23A defines emission areas 24, whichare not covered with the (first) light blocking layer 23A. In otherwords, areas other than the emission areas 24 are covered with the(first) light blocking layer 23A. In the embodiment, the light guidinglayer 25 is entirely formed in the emission areas 24.

In the embodiment, the (first) light blocking layer 23A has a thicknessgreater than the light guiding layer 25. Further, the light guidinglayer 25 has a thickness greater than the microLEDs 22 as shown in FIG.3B. In another embodiment, however, the light guiding layer 25 has athickness less than or equal to the microLEDs 22.

FIG. 3C shows a cross-sectional view of a top emission microLED display300 according to a modified second embodiment of the present invention.In the embodiment shown in FIG. 3C, the (first) light blocking layer 23Ahas a thickness less than the light guiding layer 25. Moreover, the(first) light blocking layer 23A and the light guiding layer 25partially overlap each other, and the (first) light blocking layer 23Ais partially covered with the light guiding layer 25.

FIG. 3D shows another top view of the top emission microLED display 300according to the second embodiment of the present invention. Aconnecting structure 26, such as conductive electrode, is disposed on atop surface of the microLED 22 in each emission area 24. According toone aspect of the embodiment, the connecting structures 26 in theemission areas 24 have the same pattern and the connecting structures 26in each emission area 24 have the same pattern, which can preventnonuniform display issue.

FIG. 4A shows a top view of a top emission microLED display 400according to a third embodiment of the present invention, and FIG. 4Bshows a cross-sectional view of FIG. 4A. In the embodiment, microLEDs 22(e.g., red microLED 22R, green microLED 22G and blue microLED 22B) maybe disposed above a (first) main substrate 21A. Each microLED 22corresponds to an emission area 24. In the embodiment, a frame-shapedfirst light blocking layer 23A surrounds the emission area 24 and isdisposed above the (first) main substrate 21A. In the embodiment, ablocking substrate 27 is disposed above the (first) main substrate 21Aand the first light blocking layer 23A. A second light blocking layer23B, which covers areas other than the emission areas 24 and the firstlight blocking layer 23A, is disposed on a bottom surface of theblocking substrate 27. The first light blocking layer 23A and the secondlight blocking layer 23B partially overlap each other. Accordingly, anaperture d1 of the first light blocking layer 23A is different from(e.g., smaller than) an aperture d2 of the second light blocking layer23B. In another embodiment, the aperture of the first light blockinglayer 23A is greater than the aperture of the second light blockinglayer 23B. In the embodiment, the first light blocking layer 23A and thesecond light blocking layer 23B may include BM, and the blockingsubstrate 27 may include transparent material such as quartz, glass orplastic material.

A light guiding layer 25, composed of light guiding material, isdisposed in the emission areas 24 to spread the light emitted by themicroLEDs 22. In the embodiment, the light guiding layer 25 is entirelyformed in the emission areas 24.

In the embodiment, the first light blocking layer 23A has a thicknessgreater than the light guiding layer 25. Further, the light guidinglayer 25 has a thickness greater than the microLEDs 22 as shown in FIG.4B. In another embodiment, however, the light guiding layer 25 has athickness less than or equal to the microLEDs 22.

FIG. 4C shows a cross-sectional view of a top emission microLED display400 according to a modified third embodiment of the present invention.In the embodiment shown in FIG. 4C, the first light blocking layer 23Ahas a thickness less than the light guiding layer 25. Moreover, thefirst light blocking layer 23A is partially covered with the lightguiding layer 25.

According to one aspect of the embodiment, the connecting structures 26(not shown) in each emission area 24 have the same pattern, which canprevent nonuniform display issue.

FIG. 5A shows a top view of a top emission microLED display 500according to a fourth embodiment of the present invention, and FIG. 5Bshows a cross-sectional view of FIG. 5A. The fourth embodiment issimilar to the third embodiment with the exception that, in the fourthembodiment, the first light blocking layer 23A and the second lightblocking layer 23B are disposed between adjacent pixels (instead ofadjacent microLEDs 22) to prevent interference (e.g., color mixing)between adjacent pixels and to enhance contrast.

In the embodiment, each pixel (which includes red microLED 22R, greenmicroLED 22G and blue microLED 22B) corresponds to an emission area 24.In the embodiment, a frame-shaped first light blocking layer 23Asurrounds the emission area 24 and is disposed above the (first) mainsubstrate 21A. In the embodiment, a second light blocking layer 23B,which covers areas other than the emission areas 24 and the first lightblocking layer 23A, is disposed on a bottom surface of the blockingsubstrate 27. The first light blocking layer 23A and the second lightblocking layer 23B partially overlap each other. Accordingly, anaperture d1 of the first light blocking layer 23A is different from(e.g., smaller than) an aperture d2 of the second light blocking layer23B. In the embodiment, the first light blocking layer 23A and thesecond light blocking layer 23B may include BM, and the blockingsubstrate 27 may include transparent material such as quartz, glass orplastic material.

A light guiding layer 25, composed of light guiding material, isdisposed in the emission areas 24 to spread the light emitted by themicroLEDs 22. In the embodiment, the light guiding layer 25 is entirelyformed in the emission areas 24.

In the embodiment, the first light blocking layer 23A has a thicknessgreater than the light guiding layer 25. Further, the light guidinglayer 25 has a thickness greater than the microLEDs 22 as shown in FIG.5B. In another embodiment, however, the light guiding layer 25 has athickness less than or equal to the microLEDs 22.

FIG. 5C shows a cross-sectional view of a top emission microLED display500 according to a modified fourth embodiment of the present invention.In the embodiment shown in FIG. 5C, the first light blocking layer 23Ahas a thickness less than the light guiding layer 25. Moreover, thefirst light blocking layer 23A is partially covered with the lightguiding layer 25.

According to one aspect of the embodiment, the connecting structures 26(not shown) in the emission areas 24 have the same pattern and theconnecting structures 26 in each emission area 24 have the same pattern,which can prevent nonuniform display issue.

FIG. 6 shows a cross-sectional view of a top emission microLED display600 according to a fifth embodiment of the present invention. In theembodiment, the top emission microLED display 600 may include a firstmain substrate 21A and a second main substrate 21B, which are disposedat a same level but correspond to distinct microLED displays,respectively. A first light blocking layer 23A is disposed above thefirst main substrate 21A and the second main substrate 21B. Similar tothe fourth embodiment, the top emission microLED display 600 may includea second light blocking layer 23B, which covers areas other than theemission areas 24 and the first light blocking layer 23A, being disposedon a bottom surface of the blocking substrate 27. As shown in FIG. 6,the first main substrate 21A and the second main substrate 21Bcorrespond to the same blocking substrate 27, and the first lightblocking layer 23A of the first main substrate 21A and the second lightblocking layer 23B of the second main substrate 21B correspond to thesame second light blocking layer 23B at a joint of the first mainsubstrate 21A and the second main substrate 21B. Accordingly, multiplemicroLED displays may be joined to become a seamless top emissionmicroLED display 600.

FIG. 7A to FIG. 13B show top views and cross-sectional viewsillustrating steps of forming a top emission microLED display accordingto one embodiment of the present invention. As shown in FIG. 7A and FIG.7B, a (first) main substrate 21A, which defines an emission area 24, isprovided. As shown in FIG. 8A and FIG. 8B, a bottom common electrodelayer 28 is formed on a top surface of the (first) main substrate 21A.According to one aspect of the embodiment, the bottom common electrodelayer 28 entirely covers the emission area 24 to prevent nonuniformdisplay issue.

As shown in FIG. 9A and FIG. 9B, microLEDs 12 (e.g., red microLED 12R,green microLED 12G and blue microLED 12B) are disposed on a top surfaceof the bottom common electrode layer 28 by a bonding technique. As shownin FIG. 10A and FIG. 10B, a (first) light blocking layer 23A is disposedin an area other than the emission area 24 to prevent interference(e.g., color mixing) between adjacent pixels and to enhance contrast.

As shown in FIG. 11A and FIG. 11B, a light guiding layer 25 is disposedin the emission areas 24 to spread the light emitted by the microLEDs22. In the embodiment, the light guiding layer 25 is entirely formed inthe emission areas 24. The light guiding layer 25 has a thicknessgreater than the microLEDs 22 as shown in FIG. 11B. In anotherembodiment, however, the light guiding layer 25 has a thickness lessthan or equal to the microLEDs 22. It is noted that the order of formingthe (first) light blocking layer 23A (FIG. 10A and FIG. 10B) and formingthe light guiding layer 25 (FIG. 11A and FIG. 11B) may be exchanged.

As shown in FIG. 12A and FIG. 12B, contact holes are formed above themicroLEDs 22. Next, as shown in FIG. 13A and FIG. 13B, connectingstructures 26 are formed to connect the microLED 22. The connectingstructures 26 have the same pattern and the connecting structures 26 ineach emission area 24 have the same pattern, which can preventnonuniform display issue.

FIG. 14 schematically shows a side view of a bottom emission microlight-emitting diode (microLED) display 1400. In the embodiment,microLEDs 12 (e.g., red microLED 12R, green microLED 12G and bluemicroLED 12B) may be disposed above a main substrate 11 by a bondingtechnique. As the microLEDs 12 emit light downward (as shown by arrows)against the top surface of the main substrate 11, the display 1400 iscalled a bottom emission microLED display. In the specification, themicroLEDs 12 have a size of 1-10 micrometers, which may be decreased orincreased according to specific applications or technologicaldevelopment in the future.

FIG. 15A shows a top view of a bottom emission microLED display 1500according to a sixth embodiment of the present invention, and FIG. 15Bshows a cross-sectional view of FIG. 15A. In the embodiment, microLEDs22 (e.g., red microLED 22R, green microLED 22G and blue microLED 22B)may be disposed on a top surface of a (first) main substrate 21A. A(first) light blocking layer 23A is disposed between adjacent microLEDs22 and above the (first) main substrate 21A to prevent interference(e.g., color mixing) between adjacent microLEDs 22 and to enhancecontrast. A top common electrode layer 28 may be disposed above themicroLEDs 22 and the light blocking layer 23A.

The (first) light blocking layer 23A of the embodiment may include blackmatrix (BM). In the embodiment shown in FIG. 15B, black resin is firstformed, followed by adopting photo process and curing process to formthe BM (first) light blocking layer 23A. In another embodiment, ink-jetprinting technique and curing process are adopted to form the BM (first)light blocking layer 23A.

The (first) light blocking layer 23A defines emission areas 24, whichare not covered with the (first) light blocking layer 23A. In otherwords, areas other than the emission areas 24 are covered with the(first) light blocking layer 23A. A light guiding layer 25, composed oflight guiding material, is disposed in the emission areas 24 to spreadthe light emitted by the microLEDs 22. The light guiding material istransparent with high refractive index. In the embodiment, the lightguiding layer 25 is entirely formed in the emission areas 24.

In the embodiment, the (first) light blocking layer 23A has a thicknessgreater than the light guiding layer 25. Further, the light guidinglayer 25 has a thickness greater than the microLEDs 22 as shown in FIG.15B. In another embodiment, however, the light guiding layer 25 has athickness less than or equal to the microLEDs 22.

FIG. 15C shows a cross-sectional view of a bottom emission microLEDdisplay 1500 according to a modified sixth embodiment of the presentinvention. In the embodiment shown in FIG. 15C, the (first) lightblocking layer 23A has a thickness less than the light guiding layer 25.Moreover, the (first) light blocking layer 23A and the light guidinglayer 25 partially overlap each other, and the (first) light blockinglayer 23A is partially covered with the light guiding layer 25. In theembodiment shown in FIG. 15C, a chromium/chromium oxide film is firstformed, followed by adopting photo etching technique to form the BM(first) light blocking layer 23A.

FIG. 15D shows another top view of the bottom emission microLED display1500 according to the sixth embodiment of the present invention. Aconnecting structure 26, such as conductive electrode, is disposedbetween the microLEDs 22 and the main substrate 21A in each emissionarea 24. The connecting structure may include transparent material(e.g., indium tin oxide), opaque material (e.g., metal) or reflectivematerial. According to one aspect of the embodiment, the connectingstructures 26 in the emission areas 24 have the same pattern, which canprevent nonuniform display issue.

FIG. 16A shows a top view of a bottom emission microLED display 1600according to a seventh embodiment of the present invention, and FIG. 16Bshows a cross-sectional view of FIG. 16A. The seventh embodiment issimilar to the sixth embodiment with the exception that, in the seventhembodiment, the (first) light blocking layer 23A is disposed betweenadjacent pixels (instead of adjacent microLEDs 22) to preventinterference (e.g., color mixing) between adjacent pixels and to enhancecontrast.

The (first) light blocking layer 23A defines emission areas 24, whichare not covered with the (first) light blocking layer 23A. In otherwords, areas other than the emission areas 24 are covered with the(first) light blocking layer 23A. In the embodiment, the light guidinglayer 25 is entirely formed in the emission areas 24.

In the embodiment, the (first) light blocking layer 23A has a thicknessgreater than the light guiding layer 25. Further, the light guidinglayer 25 has a thickness greater than the microLEDs 22 as shown in FIG.16B. In another embodiment, however, the light guiding layer 25 has athickness less than or equal to the microLEDs 22.

FIG. 16C shows a cross-sectional view of a bottom emission microLEDdisplay 1600 according to a modified seventh embodiment of the presentinvention. In the embodiment shown in FIG. 16C, the (first) lightblocking layer 23A has a thickness less than the light guiding layer 25.Moreover, the (first) light blocking layer 23A and the light guidinglayer 25 partially overlap each other, and the (first) light blockinglayer 23A is partially covered with the light guiding layer 25.

FIG. 16D shows another top view of the bottom emission microLED display1600 according to the seventh embodiment of the present invention. Aconnecting structure 26, such as conductive electrode, is disposed on atop surface of the microLED 22 in each emission area 24. According toone aspect of the embodiment, the connecting structures 26 in theemission areas 24 have the same pattern and the connecting structures 26in each emission area 24 have the same pattern, which can preventnonuniform display issue.

FIG. 17A shows a top view of a bottom emission microLED display 1700according to an eighth embodiment of the present invention, and FIG. 17Bshows a cross-sectional view of FIG. 17A. In the embodiment, microLEDs22 (e.g., red microLED 22R, green microLED 22G and blue microLED 22B)may be disposed above a (first) main substrate 21A. Each microLED 22corresponds to an emission area 24. In the embodiment, a frame-shapedfirst light blocking layer 23A surrounds the emission area 24 and isdisposed above the (first) main substrate 21A. In the embodiment, ablocking substrate 27 is disposed below the (first) main substrate 21A.A second light blocking layer 23B, which covers areas other than theemission areas 24 and the first light blocking layer 23A, is disposed ona top surface of the blocking substrate 27. The first light blockinglayer 23A and the second light blocking layer 23B partially overlap eachother. Accordingly, an aperture d1 of the first light blocking layer 23Ais different from (e.g., smaller than) an aperture d2 of the secondlight blocking layer 23B. In another embodiment, the aperture of thefirst light blocking layer 23A is greater than the aperture of thesecond light blocking layer 23B. In the embodiment, the first lightblocking layer 23A and the second light blocking layer 23B may includeBM, and the blocking substrate 27 may include transparent material suchas quartz, glass or plastic material.

A light guiding layer 25, composed of light guiding material, isdisposed in the emission areas 24 to spread the light emitted by themicroLEDs 22. In the embodiment, the light guiding layer 25 is entirelyformed in the emission areas 24.

In the embodiment, the first light blocking layer 23A has a thicknessgreater than the light guiding layer 25. Further, the light guidinglayer 25 has a thickness greater than the microLEDs 22 as shown in FIG.17B. In another embodiment, however, the light guiding layer 25 has athickness less than or equal to the microLEDs 22.

FIG. 17C shows a cross-sectional view of a bottom emission microLEDdisplay 1700 according to a modified eighth embodiment of the presentinvention. In the embodiment shown in FIG. 17C, the first light blockinglayer 23A has a thickness less than the light guiding layer 25.Moreover, the first light blocking layer 23A is partially covered withthe light guiding layer 25.

According to one aspect of the embodiment, the connecting structures 26(not shown) in each emission area 24 have the same pattern, which canprevent nonuniform display issue.

FIG. 18A shows a top view of a bottom emission microLED display 1800according to a ninth embodiment of the present invention, and FIG. 18Bshows a cross-sectional view of FIG. 18A. The ninth embodiment issimilar to the eighth embodiment with the exception that, in the ninthembodiment, the first light blocking layer 23A and the second lightblocking layer 23B are disposed between adjacent pixels (instead ofadjacent microLEDs 22) to prevent interference (e.g., color mixing)between adjacent pixels and to enhance contrast.

In the embodiment, each pixel (which includes red microLED 22R, greenmicroLED 22G and blue microLED 22B) corresponds to an emission area 24.In the embodiment, a frame-shaped first light blocking layer 23Asurrounds the emission area 24 and is disposed above the (first) mainsubstrate 21A. In the embodiment, a second light blocking layer 23B,which covers areas other than the emission areas 24 and the first lightblocking layer 23A, is disposed on a top surface of the blockingsubstrate 27. The first light blocking layer 23A and the second lightblocking layer 23B partially overlap each other. Accordingly, anaperture d1 of the first light blocking layer 23A is different from(e.g., smaller than) an aperture d2 of the second light blocking layer23B. In the embodiment, the first light blocking layer 23A and thesecond light blocking layer 23B may include BM, and the blockingsubstrate 27 may include transparent material such as quartz, glass orplastic material.

A light guiding layer 25, composed of light guiding material, isdisposed in the emission areas 24 to spread the light emitted by themicroLEDs 22. In the embodiment, the light guiding layer 25 is entirelyformed in the emission areas 24.

In the embodiment, the first light blocking layer 23A has a thicknessgreater than the light guiding layer 25. Further, the light guidinglayer 25 has a thickness greater than the microLEDs 22 as shown in FIG.18B. In another embodiment, however, the light guiding layer 25 has athickness less than or equal to the microLEDs 22.

FIG. 18C shows a cross-sectional view of a bottom emission microLEDdisplay 1800 according to a modified ninth embodiment of the presentinvention. In the embodiment shown in FIG. 18C, the first light blockinglayer 23A has a thickness less than the light guiding layer 25.Moreover, the first light blocking layer 23A is partially covered withthe light guiding layer 25.

According to one aspect of the embodiment, the connecting structures 26(not shown) in the emission areas 24 have the same pattern and theconnecting structures 26 in each emission area 24 have the same pattern,which can prevent nonuniform display issue.

FIG. 19 shows a cross-sectional view of a bottom emission microLEDdisplay 1900 according to a tenth embodiment of the present invention.In the embodiment, the bottom emission microLED display 1900 may includea first main substrate 21A and a second main substrate 21B, which aredisposed at a same level but correspond to distinct microLED displays,respectively. A first light blocking layer 23A is disposed above thefirst main substrate 21A and the second main substrate 21B. Similar tothe ninth embodiment, the bottom emission microLED display 1900 mayinclude a second light blocking layer 23B, which covers areas other thanthe emission areas 24 and the first light blocking layer 23A, beingdisposed on a top surface of the blocking substrate 27. As shown in FIG.19, the first main substrate 21A and the second main substrate 21Bcorrespond to the same blocking substrate 27, and the first lightblocking layer 23A of the first main substrate 21A and the second lightblocking layer 23B of the second main substrate 21B correspond to thesame second light blocking layer 23B at a joint of the first mainsubstrate 21A and the second main substrate 21B. Accordingly, multiplemicroLED displays may be joined to become a seamless bottom emissionmicroLED display 1900.

FIG. 20A to FIG. 26B show top views and cross-sectional viewsillustrating steps of forming a bottom emission microLED displayaccording to one embodiment of the present invention. As shown in FIG.20A and FIG. 20B, a (first) main substrate 21A, which defines anemission area 24, is provided. As shown in FIG. 21A and FIG. 21B,connecting structures 26 are formed to connect the microLED 22. Theconnecting structures 26 have the same pattern and the connectingstructures 26 in each emission area 24 have the same pattern, which canprevent nonuniform display issue.

As shown in FIG. 22A and FIG. 22B, microLEDs 12 (e.g., red microLED 12R,green microLED 12G and blue microLED 12B) are disposed on a top surfaceof the bottom common electrode layer 28 by a bonding technique. As shownin FIG. 23A and FIG. 23B, a (first) light blocking layer 23A is disposedin an area other than the emission area 24 to prevent interference(e.g., color mixing) between adjacent pixels and to enhance contrast.

As shown in FIG. 24A and FIG. 24B, a light guiding layer 25 is disposedin the emission areas 24 to spread the light emitted by the microLEDs22. In the embodiment, the light guiding layer 25 is entirely formed inthe emission areas 24. The light guiding layer 25 has a thicknessgreater than the microLEDs 22 as shown in FIG. 24B. In anotherembodiment, however, the light guiding layer 25 has a thickness lessthan or equal to the microLEDs 22. It is noted that the order of formingthe (first) light blocking layer 23A (FIG. 23A and FIG. 23B) and formingthe light guiding layer 25 (FIG. 24A and FIG. 24B) may be exchanged.

As shown in FIG. 25A and FIG. 25B, contact holes are formed above themicroLEDs 22. Next, as shown in FIG. 26A and FIG. 26B, a top commonelectrode layer 28 is formed above the light guiding layer 25. Accordingto one aspect of the embodiment, the top common electrode layer 28entirely covers the emission area 24 to prevent nonuniform displayissue.

FIG. 27 shows a cross-sectional view of a bottom emission microLEDdisplay 2000 according to an eleventh embodiment of the presentinvention. Compared to FIG. 19, the bottom emission microLED display2000 of the present embodiment may include at least one shielding layer30 for blocking electromagnetic interference (EMI). In one embodiment,the shielding layer 30 may include transparent conductive material suchas transparent conductive oxide (e.g., indium tin oxide (ITO), indiumzinc oxide (IZO) or aluminum doped Zinc Oxide (AZO)).

The shielding layer 30 may be disposed between a top surface of thefirst main substrate 21A and first light blocking layer 23A. Theshielding layer 30 may be electrically insulated from the top commonelectrode layer 28 by an insulating layer 29, and may be electricallyinsulated from the connecting structure 26 by an insulating layer 31.Similarly, the shielding layer 30 may be disposed between a top surfaceof the second main substrate 21B and first light blocking layer 23A. Theshielding layer 30 may be electrically insulated from the top commonelectrode layer 28 by an insulating layer 29, and may be electricallyinsulated from the connecting structure 26 by an insulating layer 31.The shielding layer 30 may be disposed between a top surface of theblocking substrate 27 and the second light blocking layer 23B. Generallyspeaking, the shielding layer 30 may be disposed in one or more areasmentioned above.

The shielding layer 30 may be adaptable to a top emission microLEDdisplay. FIG. 28 shows a cross-sectional view of a top emission microLEDdisplay 2100 according to a twelfth embodiment of the present invention.Compared to FIG. 6, the top emission microLED display 2100 of thepresent embodiment may include at least one shielding layer 30 forblocking electromagnetic interference (EMI). In one embodiment, theshielding layer 30 may include transparent conductive material such astransparent conductive oxide (e.g., indium tin oxide (ITO), indium zincoxide (IZO) or aluminum doped Zinc Oxide (AZO)). In the embodiment, theshielding layer 30 may be disposed between a bottom surface of theblocking substrate 27 and the second light blocking layer 23B.

FIG. 29 shows a cross-sectional view of a bottom emission microLEDdisplay 2900 according to a thirteenth embodiment of the presentinvention. Compared to FIG. 15B, the bottom emission microLED display2900 of the present embodiment may include an anti-floodlight layer 32disposed on a bottom surface of the first main substrate 21A and betweenadjacent microLEDs 22. In other words, the anti-floodlight layer 32 maybe disposed on the first main substrate 21A opposite the (first) lightblocking layer 23A. FIG. 30 shows a cross-sectional view of a bottomemission microLED display 2900 according to a modified thirteenthembodiment of the present invention. Compared to FIG. 15C, the bottomemission microLED display 2900 of the present embodiment may include ananti-floodlight layer 32 disposed on a bottom surface of the first mainsubstrate 21A and between adjacent microLEDs 22. In other words, theanti-floodlight layer 32 may be disposed on the first main substrate 21Aopposite the (first) light blocking layer 23A.

After the light emitted by the microLEDs 22 enters the first mainsubstrate 21A, some of the generated light passes through the first mainsubstrate 21A, while other of the generated light laterally diffuses inthe first main substrate 21A due to total reflection, which mayinterfere with adjacent microLED 22 or pixel to result in floodlightissue. The anti-floodlight layer 32 of the embodiment may absorb lateraldiffused light and effectively avoid floodlight issue.

The anti-floodlight layer 32 of the embodiment may include BM. In oneexample, a chromium/chromium oxide film is first formed, followed byadopting photo etching technique to form the BM anti-floodlight layer32. In another example, black resin is first formed, followed byadopting photo process and curing process to form the BM anti-floodlightlayer 32. In a further example, ink-jet printing technique and curingprocess are adopted to form the BM anti-floodlight layer 32. Theanti-floodlight layer 32 may be directly formed on the first mainsubstrate 21A, or may be first formed on another substrate, which isthen attached on the first main substrate 21A.

As discussed above, the anti-floodlight layer 32 may be disposed betweenadjacent microLEDs 22. However, the anti-floodlight layer 32 may bedisposed between adjacent pixels. FIG. 31 shows a cross-sectional viewof a bottom emission microLED display 3100 according to a fourteenthembodiment of the present invention. Compared to the seventh embodimentshown in FIG. 16B, the bottom emission microLED display 3100 of thepresent embodiment may include an anti-floodlight layer 32 disposed on abottom surface of the first main substrate 21A and between adjacentpixels. In other words, the anti-floodlight layer 32 may be disposed onthe first main substrate 21A opposite the (first) light blocking layer23A. FIG. 32 shows a cross-sectional view of a bottom emission microLEDdisplay 3100 according to a modified fourteenth embodiment of thepresent invention.

Compared to the modified seventh embodiment shown in FIG. 16C, thebottom emission microLED display 3100 of the present embodiment mayinclude an anti-floodlight layer 32 disposed on a bottom surface of thefirst main substrate 21A and between adjacent pixels. In other words,the anti-floodlight layer 32 may be disposed on the first main substrate21A opposite the (first) light blocking layer 23A.

Although specific embodiments have been illustrated and described, itwill be appreciated by those skilled in the art that variousmodifications may be made without departing from the scope of thepresent invention, which is intended to be limited solely by theappended claims.

What is claimed is:
 1. A bottom emission microLED display, comprising: afirst main substrate; a plurality of microLEDs disposed above the firstmain substrate; a first light blocking layer disposed above the firstmain substrate to define a plurality of emission areas; a light guidinglayer disposed in the plurality of emission areas; a plurality ofconnecting structures disposed in the plurality of emission areasrespectively and electrically connected with the microLEDs; a top commonelectrode layer disposed above the first light blocking layer and themicroLEDs; a blocking substrate disposed below the first main substrate;a second light blocking layer formed on a top surface of the blockingsubstrate, the second light blocking layer covering areas other than theplurality of emission areas and the first light blocking layer; and asecond main substrate disposed at a same level as the first mainsubstrate, the first main substrate and the second main substratecorresponding to distinct microLED displays respectively, and the firstlight blocking layer being disposed above the first main substrate andthe second main substrate; wherein the first light blocking layersurrounding each of the plurality of emission areas has a frame shape,the first light blocking layer and the second light blocking layerpartially overlapping each other; wherein the first main substrate andthe second main substrate correspond to the same blocking substrate, andthe first light blocking layer of the first main substrate and thesecond light blocking layer of the second main substrate correspond tothe same second light blocking layer at a joint of the first mainsubstrate and the second main substrate.
 2. The display of claim 1,wherein the plurality of connecting structures have a same pattern. 3.The display of claim 1, wherein the plurality of connecting structurescomprise transparent material.
 4. The display of claim 1, wherein theplurality of connecting structures comprise opaque material.
 5. Thedisplay of claim 1, wherein the first light blocking layer comprisesblack matrix.
 6. The display of claim 1, wherein the first lightblocking layer has a thickness greater than the light guiding layer. 7.The display of claim 1, wherein each of the plurality of emission areascorresponds to a red microLED, a green microLED and a blue microLED. 8.The display of claim 1, wherein a red microLED, a green microLED and ablue microLED in each of the plurality of emission areas respectivelycorrespond to the plurality of connecting structures with a samepattern.
 9. The display of claim 1, wherein the plurality of connectingstructures are entirely formed in the emission areas.
 10. The display ofclaim 1, further comprising a shielding layer disposed between the firstmain substrate and the first light blocking layer for blockingelectromagnetic interference.
 11. The display of claim 10, wherein theshielding layer comprises transparent material.
 12. The display of claim1, wherein an aperture of the first light blocking layer is differentfrom an aperture of the second light blocking layer.
 13. The display ofclaim 1, wherein the second light blocking layer comprises black matrix.14. The display of claim 1, wherein the blocking substrate comprisestransparent material.
 15. The display of claim 1, further comprising ashielding layer disposed between the blocking substrate and the secondlight blocking layer for blocking electromagnetic interference.
 16. Thedisplay of claim 15, wherein the shielding layer comprises transparentmaterial.
 17. The display of claim 1, further comprising a shieldinglayer disposed between the second main substrate and the first lightblocking layer for blocking electromagnetic interference.
 18. Thedisplay of claim 17, wherein the shielding layer comprises transparentmaterial.
 19. The display of claim 1, the microLED is a rectangle and isdisposed longitudinally.